Patent GB-584417-A (GB)
Title: Improvements relating to electric circuit breakers and indicating devices therefor
IPC: H01H13/02
Filed: 1944-12-08
Abstract: 584,417. Indicators for switches; switches, partly electromagnetic; press-button switches. C.A.V., Ltd., and CURZON, T. Dec. 8, 1944, No. 24619. [Class 38 (v)] An automatic circuit-breaker is provided with a signal lamp and a two-way switch which in one position indicates that the breaker is in working order and in the other position enables the lamp to be used for testing the continuity of the circuit controlled by the breaker. Fig. 1 shows the connections between the lamp j the switch and the circuit breaker contacts e, f. The lamp is connected between a spring contact a and a movable contact c of the two-way switch the fixed contacts b, d of which are connected across the circuit controlled by the breaker. The contact c is carried by a push button i through which the light from the lamp is visible. A manually operated switch k is in series with the contacts e, f and when these contacts and the switch k are closed the lamp is short-circuited. If however the contacts e, f or the switch k are opened separately and the contact c brought into contact with the contacts b and d respectively the lamp is illuminated. Failure of the lamp to light indicates a fault and if, for example, the switch k is opened and the contacts e, f closed and no current passes through the lamp when the contacts c, d are joined a break in the circuit is indicated. Fig. 2 shows a circuit breaker operated by a bimetallic strip u in combination with a testing lamp j and a two-way switch actuated by a press button i. The contacts e, f of the circuit breaker are carried by the armature s of an electromagnet q and the strip u respectively. The electromagnet comprises metal frame members p, p<1> the latter being electrically connected to the adjacent end of the core r while the member p and a plate w carry terminal screws x for connection to the circuit to be controlled. The plate w is insulated from the core r and carries an extension v to which the strip u is connected, the armature s being hingedly attached to a plate t which is electrically connected to the core r. The ends of the core winding are connected to the plates t, w. The circuit from the plate w through the extension v, contacts f, e, plate t, core r and plate p' to the plate p' is completed and interrupted by a switch k which comprises a knob 6 carrying connected contacts 3 which are spring supported and which can be snapped into engagement with fixed contacts 2 by pulling the knob 6. The contacts 2 are connected to the plates p, p<1>. Under normal conditions the contacts e, f are closed and short-circuit the winding of the electromagnet which has a high resistance. If a short-circuit occurs in the controlled circuit the strip u is heated and separates the contacts e, f whereupon current flows through the electromagnet winding causing the armature s to complete the separation rapidly and to prevent the contacts from closing again till the switch k is opened. The two-way switch operated by the push button i and the indicating lamp j are housed within the casing of the circuit breaker, the contact a being connected to the core r, the contact b consisting of two lugs extending from the plate w. Contact d is joined to the frame member p while the movable contact c comprises two projections extending from a yoke h carried by the button i and pressing against the upper terminal of the lamp. The lamp can be removed by turning it till the projections forming the contact c are freed from the lugs b and then lifting it clear of the casing o.